Circadian formation of clock protein complexes by KaiA, KaiB, KaiC, and SasA in cyanobacteria

Hakuto Kageyama, Takao Kondo, Hideo Iwasaki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

111 Citations (Scopus)


Physical interactions among clock-related proteins KaiA, KaiB, KaiC, and SasA are proposed to be important for circadian function in the cyanobacterium Synechococcus elongatus PCC 7942. Here we show that the Kai proteins and SasA form heteromultimeric protein complexes dynamically in a circadian fashion. KaiC forms protein complexes of ∼350 and 400-600 kDa during the subjective day and night, respectively, and serves as a core of the circadian protein complexes. This change in the size of the KaiC-containing complex is accompanied by nighttime-specific interaction of KaiA and KaiB with KaiC. In various arrhythmic mutants that lack each functional Kai protein or SasA, circadian rhythms in formation of the clock protein complex are abolished, and the size of the protein complexes is dramatically affected. Thus, circadian-regulated formation of the clock protein complexes is probably a critical process in the generation of circadian rhythm in cyanobacteria.

Original languageEnglish
Pages (from-to)2388-2395
Number of pages8
JournalJournal of Biological Chemistry
Issue number4
Publication statusPublished - 2003 Jan 24
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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